Poly -functionalized divinyl

Figure 4 Crossover of peak retention times as a function of gradient rate in the separation of peptides. (Previously unpublished data are drawn from Swadesh, J. K., Tryptic fingerprinting on a poly(styrene-divinyl benzene) reversed phase column, /. Chromatogr., 512, 3215, 1990.92)...

Hydrogels were synthesized by cross-linking HA with DVS and poly (ethylene glycol)-functionalized divinyl sulfone (VS-PEG-VS). These gels were loaded with vitamin E succinate (VES) and bovine serum albumin (BSA), as models of antiinflammatory proteins and drugs, and their release kinetics were measured in vitro. The rate of release from HA-VS-PEG-VS-HA hydrogels was faster than that from HA-DVS-HA hydrogels, presumably because of the lower cross-linked density in the former (75). 

Elastomeric networks with junction functionalities ranging from 4 to 70 were prepared by endlinking a,u)-divinyl poly(dimethylsiloxane) chains having number average molecular weights ranging from 8,800 to 55,300 with polyfunctional junctions provided by linear and branched poly(methylhydrogensiloxanes). 

In earlier work preformed polymer was cross-linked, e.g. by ionizing radiation (39, 103, 104) with suitable assumptions as to randomness of the reaction, the molecular statistics of product can be calculated as a function of the degree of cross-linking. An alternative method is to co-polymerize with small amounts of tetra-functional monomer, e.g. divinyl benzene (36, 105, 107). Both these methods produce highly poly-disperse products, having tetra-functional branch-points. 

L-24 as a ligand, up to 85—90% yield. The linking reaction of a poly(tBA) with a bromide terminal was also possible with divinylbenzene, whereas the other two divinyl compounds led to side reactions.328 The yield of star polymers can be increased up to 95% with the use of additives. The a-end-functionalized linear polymers afford surface-functionalized star polymers with various functional groups such as alcohols, amines, epoxides, and nitriles. 

Similarly, a telechelic polymer bearing carboxylic acid groups at both chain ends was formed by carrying out the lipase-catalyzed polymerization of DDL in the presence of divinyl sebacate [72]. In this case, divinyl sebacate functioned as a coupling agent creating poly(DDL) chains with hydroxyl groups at both termini. 

Functionalized XE-30S (a 3% cross-linked macroporous polystyrene with most probable pore size 130 nm), XAD-4 (a poly(divinylbenzene) with surface area >700 m /g and most probable pore size <5 nm), and PSP-12 (a macroporous poly(divinyl-benzene) with most probable pore size <5 nm) also have been studied by scanning electron micn robe (22)- Chloromethylation proceeded uniformly thro hout all three polymers. Reaction with lithium diphenylphosphide for 18 h in THF at room temperature, and photochemical metalation with phenanthrenechromium tricarbonyl, proceeded uniformly in XE-305, but primarily near the surfaces of XAD-4 and PSP-12. 

The field of organic chemistry has seen the most extensive use of polymeric materials as aids in effecting chemical transformation and product isolation. Insoluble polymer supports have been used as handles to facilitate these functions. As chemical reagents can be bound to an insoluble polymer carrier and used in organic synthesis [117,118], polymer-bound reagents can also be used to assist in the purification step of solution-phase reactions [119,120]. The latter are known as scavenger resins. These are added to the reaction mixture upon completion of the reaction in order to quench and selectively bind to the unreacted reagents or by-products. The polymer-bound impurities are then removed firom the product by simple filtration to obtain pure compounds. For example, aminomethylated poly(styrene-co-divinyl benzene) can be used to remove acid chlorides, sulfonyl chlorides, isocyanates, thiocyanates, and proton. Similarly, 2-Chlorotrityl resins have been developed for the attachment of carboxylic acids, alcohols. 

Multiarm polymers (11) can be prepared that still have the reactive functional groups (Z) close to the core. As these are still active, they can be used as sites to initiate the growth of more arms by adding either the same monomer used to prepare (11) or a second monomer to prodnce mikto-arm star polymers, in which the arms have different chemical structures. Thus, an active ended poly(t-butyl acrylate), prepared by ATRP, can be coupled with divinyl benzene to form a multiann star polymer. This structure can be converted to a mikto-arm star polymer by reacting the living ends still present with n-butyl acrylate, and so propagate poly(n-butyl acrylate) chains from the core outward. 

Figure 10-23. Glass transition temperature as a function of the reciprocal number average molar mass for linear,/ = 2, and star-shaped branched poly(styrenes) with/ = 3 or/ = 10-12 arms, as well as for poly(styrenes) cross-linked with divinyl benzene with mean degrees of cross-linking per chain of/= 3, 5-7, or 10-12 (according to data from F. Rietsch, D. Daveloose and D. Froelich).

Fig. 19 Thermally induced collapse of poly(A, Af-diethylacrylamide) hydrogel (curve 1) and cryogel samples (curve 2) upon increasing the temperature from room temperatiffe to 60 °C. The variation in the volume of the gel samples is shown as a function of the deswelling time. Synthesis conditions initial monomer concentration 5.66 wt% molar ratio of vinyl to divinyl monomers 200 1 gelation temperature +20 °C (curve 1) and — 10 C (curve 2). (From [172] with permission from Springer)...

R. BakryandG. K. Bonn, Monolithic poly(glycidyl methacrylatedivinyl-benzene) capillary columns functionalized to strong anion exchangers for nucleotide and oligonucleotide separation,/. Sep. Sci. 16. 2478-2484. 2006. 

Phase Separation and Gelation Studies. A phase diagram of linear poly(ethylene oxide) (LPEO) and divinyl benzene (DVB) cross-linked poly(methyl methacrylate) as a function of polymerization of the latter was also researched hy duPrez and co-workers (49) (Fig. 11). The temperature of measurement was also a variable, but the curve separating the one-phased system from the two-phased system did not change much in the narrow temperature range covered. 

Employing a similar approach as above, thiol-terminated RAFT polymers have also been reacted with a variety of low and high molecular weight acrylate species for ef cient end functionalization (Spruell et al., 2009) and immobilized onto ene-decorated microspheres of poly(divinyl benzene) (Goldmann et al., 2009). Considering the abundance of commercially available activated alkene substrates amenable to nucleophihc addition (e.g., acrylates and maleimides) and the simplicity-cum-robusrness of the aforesaid approach, the RAFT/thiol-ene combination can be expected to remain as a valuable tool for macromolecular synthesis (Sumerlin and Vogt, 2010). 

Figure 5.9 Effect of crosslinking on Tg of branched poly(styrene-co-divinyl benzene). The crosslink functionality (F) is shown adjacent to each regression line. Drawn after data from Rietsch, Daveloose and Froelich (1976).

By using RCM with the Grubbs catalyst, synthesis of cyclic poly(e-caprolactone) [poly(e-CL)] was reported by Xie et al. [75]. They used 10-undecen-l-ol as initiator to polymerize the e-CL with Sn(Oct)2 as catalyst. The hydroxyl chain end of the poly (e-CL) was further functionalized by the reaction with undecylenic acid chloride to give a divinyl poly(e-CL). The cyclization was carried out in a one-pot reaction at a polymer concentration of 5.0 x 10 " mol/L however, the efficiency of the cyclization was relatively low as their SEC traces showed a large amount of multiblock condensation by-products (Scheme 23). 

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